Renewable Energy: In Pursuit Of Zero Energy Buildings

By Anne Vazquez
Published in the March 2011 issue of Today’s Facility Manager

Energy consumption in commercial and institutional buildings will continue to increase until these structures can be designed to produce more energy than they consume. To address this issue, in 2005, the U.S. Department of Energy’s (DOE) Building Technologies Program established a goal to create the technology and knowledge base for marketable zero energy commercial buildings (ZEBs) by 2025.

To help DOE reach its ZEB goal, the Buildings and Thermal Systems Center at the National Renewable Energy Laboratory (NREL) established a study in 2006 of six buildings planned for construction in various locations in the United States. The purpose was to identify and address the issues related to the design, construction, operation, and evaluation of the current generation of low energy commercial buildings.

Those six buildings and the lessons learned helped NREL researchers to create a set of best practices for those who design and operate facilities. These lessons are now being used to guide future research on commercial buildings to meet the DOE goal of facilitating marketable ZEBs by 2025. The six buildings included in the study were:

The Thermal Test Facility (TTF), National Renewable Energy Laboratory in Golden, CO; and

BigHorn Home Improvement Center in Silverthorne, CO.

Each of these six commercial buildings studied was designed for a different function, but they shared common requirements. Each must provide visual, acoustic, and thermal comfort for its occupants. All must withstand climatic conditions, and all must meet or exceed the programmatic requirements for their spaces.

The architects and engineers on the NREL team created a strategy, which required a whole building design process. This process required that the team responsible for the building design (including the architect, engineers, energy and other consultants, facility manager, and even the occupants) worked together to set and understand the energy performance goals.

Various incarnations of the whole building design process were used to construct the buildings. For the Zion, BigHorn, and TTF buildings, the NREL team was directly involved in the design process, providing energy analysis and facilitating the process as it applied to energy performance.

All the buildings feature combinations of “off the shelf” technologies to reduce energy use and minimize environmental impacts. They all were designed with thermal envelopes that exceed current energy codes. They also use daylighting, radiant heating, natural ventilation, evaporative cooling, ground source heat pumps, photovoltaics (PV), and passive solar strategies.

The team then monitored the six buildings after they were built for at least one year and analyzed the data to determine energy performance with respect to design goals. After one year of operation, it was found that each building was consuming between 25% to 70% less energy than comparable energy code compliant buildings. However, additional energy efficiency was required for these buildings to reach DOE’s ZEB goal.

The NREL team has reported that its lessons learned, which are applicable to all the buildings in the study, are:

Facility owners/managers provide the main motivation for low energy buildings.

Setting measurable energy saving goals at the outset of a project is crucial to realizing low energy buildings.

Many decisions are not motivated by cost.

Current technologies can substantially change how buildings perform.

A whole building design approach is a good way to lower energy use and cost.

Low energy buildings do not always operate as they were designed.

While every building has requirements that differentiate it from others, the NREL team chose the six buildings in its study because it determined those represent a broad cross section. So while direct replication is not possible, building professionals can think about how technologies used in high performance buildings might adapt to their projects.

Research for this article included information from NREL’s technical report, “Lessons Learned from Case Studies of Six High-Performance Buildings.” For more on related research conducted by NREL, visit www.nrel.gov/buildings/comm_building_design.html.

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